What are sugar alcohols? And how they’re different than sugar

From the desk of
Robb Wolf
ScienceWhat are sugar alcohols? And how they’re different than sugar

I get a lot of questions about sugar alcohols. People want to know whether these sugar substitutes are a healthy way to satisfy a sweet tooth, and the words “sugar” and “alcohol” certainly don’t imply fitness and well-being at first glance.

But the truth is, sugar alcohols are neither sugar nor alcohol. They’re a class of sweet carbohydrates with fewer calories and health risks than sugar. And although they taste sweet, they’re not digested and metabolized like glucose, fructose, sucrose, and other compounds we broadly call “sugar.”

While they’re not the best option, sugar alcohols are uncontroversially better than sugar. In this article, I’ll cover their key advantages over sugar, as well as a few disadvantages compared to better sugar alternatives like stevia.

What Is Sugar?

The term “sugar” can refer to many molecules—glucose, fructose, sucrose, high-fructose corn syrup, and more. When someone talks about blood sugar, for instance, they’re talking about glucose. This molecule is the same carbohydrate that plants store for later use as energy. But when people say “pass the sugar,” they’re typically talking about sucrose—a combination of glucose and another simple sugar, fructose.

High-fructose corn syrup (HFCS) is the other main form of added sugar (aka “refined sugar”). Similarly to sucrose, HFCS is a blend of glucose and fructose. The main different is that it’s higher in fructose and comes in liquid form to sweeten sports drinks, fruit juices, sodas, and other sugary beverages. Being the primary source of added sugar in the American diet, HFCS is troublingly prevalent. Our whopping consumption of this high-calorie goo is linked to obesity, diabetes, and a range of other health problems.

There are a few reasons why high sugar intakes are problematic. The first is that refined sugar provides a hit of empty, non-satiating calories. You can eat (or drink) sugar almost all day and not get full. Not ideal for weight loss or weight maintenance.

Another is that a high-sugar diet puts you on the blood sugar rollercoaster. The highs are high and the lows are low. This also isn’t ideal because:

  • High blood sugar is a proinflammatory state
  • Chronically high blood sugar leads to the blood sugar regulation problems (called insulin resistance) that underlie type 2 diabetes
  • When blood sugar dips, cravings go up and energy goes down

Finally, fructose is of special concern. When you consume fructose—in fruit or refined sugar—it zooms straight to your liver for conversion to fat. This fructose-to-fat mutation served us well in Paleolithic times—it fattened us up to prepare for winter months with little available food—but with the greater volume of food available today, it’s just fattening us perpetually.

What are Sugar Alcohols?

Sugar alcohols (also called polyols) are usually derived from sugar, but they aren’t the same as sugar. They also do not contain ethanol, though I see why this is a common point of confusion.

Sugar alcohols are just sweet carbohydrates with a different chemical structure, mouthfeel, caloric load, and metabolic impact than sugar. The most common sugar alcohols are xylitol, erythritol, mannitol, sorbitol, maltitol, and lactitol.

Sugar alcohols naturally occur in grapes, mushrooms, soy sauce, and a range of other fruits, vegetables, and fermented foods. They’re also used to sweeten processed foods (ice cream, candy, cookies), chewing gum, medicines, and toothpaste.

Sugar alcohols contain fewer calories than sugar because they’re metabolized differently than sugar. Instead of coming through the small intestine, they travel to the large intestine to become dinner for gut bacteria. The exception is erythritol. Erythritol is absorbed through the small intestine and into the bloodstream, but it’s not broken down. Rather, about 90% is excreted intact through urine.

Differences Between Sugar and Sugar Alcohols

Sugar alcohols differ from sugar in several important ways. Let’s cover those now.

#1: Calories

Sugar is obesogenic largely because it adds unnecessary calories that are easy to consume in excess. Think of a big bag of Twizzlers and a 32-ounce coke at the movies. That’s about 3,500 calories of sugar in one sitting.

Getting more granular, one gram of sucrose contains 3.9 calories. Most sugar alcohols (such as xylitol and sorbitol) contain about half that amount—2 calories per gram or so.

This is because sugar alcohols are different molecules than sugar. Your body processes them differently. Most sugar alcohols aren’t absorbed in the small intestine, but rather serve as food for gut bacteria. In this way, they’re similar to dietary fiber, which is also low (or absent) in calories.

The lowest calorie sugar alcohol is erythritol, which contains only 0.2 calories per gram. Why so low? Because you pee out most of the erythritol you consume.

#2: Taste and sweetness

You already know what sucrose tastes like. Sugar alcohols taste a bit different.

They’re often described as having a “cooling sensation.” It’s why they make good sweeteners for gum, toothpaste, and ice cream.

Sugar alcohols have varying levels of sweetness:

  • Lactitol is 30-40% as sweet as sugar
  • Erythritol is 60-80% as sweet as sugar
  • Xylitol is 100% as sweet as sugar

Whether you like the taste of sugar alcohols is a matter of personal preference. I prefer the taste of stevia and monk fruit.

#3: Blood sugar effects

The glycemic index (GI) is a measure of how quickly one’s blood sugar rises in response to a given food. It goes from 0 to 100, with 100 representing the fastest blood sugar spike. Pure glucose scores 100. Sucrose scores 65. And all the sugar alcohols score 35 and below. For reference, maltitol scores 35, xylitol scores 13, and erythritol scores 0.

To be clear, the glycemic index is an imperfect measure because it doesn’t account for individual variability in our responses to food.I hammer this point home in my book Wired to Eat. For some people, a banana causes a MUCH bigger blood sugar spike than a cookie. For others, it’s the opposite. Genes matter, people.

But a food’s GI is still directionally accurate. It gives us a means of roughly comparing different foods and compounds to one another. And looking at the vast difference in GIs, sugar alcohols will almost always have a smaller blood sugar impact than sugar.

That’s why you subtract out sugar alcohols (along with fiber) when calculating net carbs on a keto diet. They don’t spike your blood sugar and insulin levels like other carbs do, so they won’t meaningfully interfere with ketosis.

Minimizing blood sugar spikes is also a good practice for general health. It’s a good way to stay metabolically flexible, keep cravings down, and reduce your risk of diabetes.

#4: Digestion

When you digest sugar, it’s broken down into glucose and fructose and absorbed through the small intestine. The fructose travels to the liver through the portal vein for conversion to fat, and the glucose ends up in your blood to be used for energy or stored as fat or glycogen for later.

Conversely, most sugar alcohols pass through the small intestine and into the large bowel to be fermented by gut bacteria. That’s why sugar alcohols have fewer calories, but it’s also why they tend to cause digestive distress.

For many folks, the fermentation of sugar alcohols causes gas, bloating, and diarrhea. In my view, this is the main drawback of these compounds.

Erythritol largely avoids this pitfall since it’s absorbed and excreted intact. While that may seem like a big plus for erythritol, it does have its own drawbacks. Recent research (2023) may indicate that erythritol increases one’s risk of cardiovascular disease. I wrote about it in another article if you’d like the full rundown.

#5: Oral health

Last but not least: cavities. Sugar causes them, while sugar alcohols prevent them. Sugar feeds a nasty bacteria in your mouth called Streptococcus mutans. Then plaques develop and cavities form.

Sugar alcohols like xylitol and erythritol have the opposite effect. They suppress the growth of S. mutans, making them favorites of dentists and oral hygienists across the globe.

One systematic review found xylitol to be “an effective strategy as a self-applied caries preventive agent.” (Dental caries is another term for cavities.) Erythritol may even be better. In one study, children were given candies sweetened with erythritol, xylitol, or sorbitol over three years. The results? Erythritol had the greatest plaque-reducing power—so even if erythritol proves to be bad for heart health, it could still serve a useful role when used orally and then spat out.

Sugar vs. Sugar Alcohols

High sugar diets are bad news. They’re a key driver of obesity, inflammation, and chronic disease in the modern world. Sugar alcohols are in a separate category. They lend sweetness without the metabolic impacts of sugar.

I believe that sugar alcohols (when tolerated) are typically a healthier sweetener than sugar. But at the end of the day, I also wouldn’t recommend them over other low-carb-friendly sweeteners like stevia or monk fruit.

That’s why I wrote a guide to the pros and cons of 12 popular sugar substitutes—so you can review the evidence for each of these sugar alternatives and pick the option that best benefits your health.

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